May 19, 2009

Maybe someone can help me with this. I have several computers, but I like using my MacBook Air around this house. It works fine with the WiFi here when I'm the only one on, but if the other person uses his MacBook (the original MacBook), it breaks my connection. Using the Network Diagnostics application, I can restore my connection, but it will break again, perhaps the every time the other user clicks from one website to another. If I get on one of my older laptops, I don't have the problem. My own old MacBook (original MacBook) interferes with my Air exactly the same way. When we're at our other house, I don't have this problem. I also have this problem at some cafés but not others.

EDH is probably correct. Your router is likely issuing the same IP address to two computers at the same time. That shouldn't happen with DHCP but its possible someone configured fixed IPs to be issued by DHCP in the router. Or maybe set the range of addresses that can be issued to be smaller than the number of computers that are in the house.

Either way - the problem is likely at the router rather than the computer. Factory reset and reconfigure might solve the problem.

- you may as well ask me to argue a case in front of the SC for all I know about such things - good luck - despite my happiness, health and money, I do little magic rituals every day to sustain my good fortune being computer dumb as I am..

Yeah, my guess is DHCP conflict. From the description it sounds like one of the machines is configured to use a static IP, which the router is then assigning to the second computer. I don't work on Macs, so can't give a step-by-step, but you should be able to tell both machines to get their IP via DHCP from the router, and that should solve it after a reboot of all machines and the router. If you still have conflicts, a reasonably advanced router should have an IP mapping table where you can tell it what IP to assign to each machine that connects to it.

You should be able to setup different access profiles on your laptops (home, roam, guest, etc.) so you can access via IP when you wish. My PC notebook is set up for three access profiles; wired, IP roaming and MAC.

Also check to make sure each machine has a unique DHCP Client ID (in System Prefs-->Network). But yeah, it sounds like the router is programmed to give out short subscriptions, and may be set to only give a limited number of connections (maybe only 1).

It could also be something else, like interference. Is the other Mac accidentally set up to share its Internet connection, which then sends out DHCP addresses from its Airport antenna?

This is a known issue, though it's rather unclear whether Apple admits it or is doing anything about it. It is a problem with OSX itself (dual boot Macs have no problems with getting kicked off WiFi when running Windows) though why is a mystery.

I don't think it's a static address thing, or it wouldn't connect lots of places.OS X is smart enough to use different configurations for each network. Thus when I'm on my home network, I have IP addr X. When I'm at work, I have IP addr Y (and IP addrs Z, A, and B on other networks).

I agree with EDH and others, it's probably router's DHCP settings. Might be a conflicting static address, or two "fixed" entries for the same address, or an insufficiently small address pool.

Or, more likely the IP address is sticky, either in your system, or some else's. This problem is really bad with Windows Vista. Not so much that you get kicked off, but rather that it just won't connect, or if it does connect, it won't run well. Why? Because Vista thinks that it is smarter than DHCP.

DHCP's primary goal in life is to assign dynamic IP addresses upon request. It does other things too, such as provide you with DNS, Wins (inapplicable for Apple), and gateway addresses, as well as some parameters such as subnet masks. Vista tries to remember the IP address you used the last time you were on a network, and then use that. And, it is often wrong.

This is what I mean though about sticky IP addresses - the computer trying to reuse an IP address from a previous session, when it really should be going to DHCP to get a new one.

Let me add that at least in the PC world, it isn't an issue with static and dynamic IP addresses. With static addresses, you assign (hard code) all the relevant addresses, masks, etc. yourself. With dynamic addresses, you are supposed to get them from DHCP. But, as noted, Vista tries to cheat here, and fails, for dynamic addresses, and this may be part of what is going on with your Mac.

Yes, it does sound like an IP address conflict, and as noted above, just using DHCP at the client level does not guarantee that you'll avoid that.

I grew so fed up with OS X (and why in heaven's name didn't they just call it "OSX", for easier Googling?) that I installed Vista on my iMac. Now I only boot to OS X to research some OS-specific question.

Vista tries to remember the IP address you used the last time you were on a network, and then use that. And, it is often wrong. It has every right to do so, if the lease time has not elapsed and it has not sent a RELEASE request to the DHCP server. If the DHCP server is re-allocating addresses it leased out and not released before the lease has elapsed, it is the server that is wrong.

I begin to suspect the hardware and/or drivers associated with your Macbook WiFi adapter. I've seen various complaints that indicate the MacBook Air may have troubles there.

If I were you, I'd try an external USB WiFi adapter on that MadBook to see if the problem goes away. It likely will. May not help and may not mean much, but at least it would tend to exculpate the router and possibly other suspects...though not with absolute certainty.

In any case, you might look for an updated driver for the machine's internal adapter. That's not necessarily easy to do, but Apple may publish one. My iMac uses Broadcom WiFi hardware, and I had to take a machete to the Internet to find a newer driver...and as I commented above, I decided in the end to go with Vista anyway. Unlike OS X, Windows both works and does the things a modern workstation OS must do.

Hallo I am using a Mac and had a similar problem. Though switching off AirPort (WiFi) and restaring always did the job I considered it not very elegant. My Solution: The problem is that Mac OS X -- at least in my configuration -- though set to get the IP Adress by DHCP is assuming to always get the same adress from the router. What I did was setting up Mac OS X to get connected by DHCP with fixed IP Adress. I configured this crappy router to assign my computer (you need the network name and it's AirPort-MAC-Numer) a fixed IP-Adress that I told Mac OS X to use.

You can do this if you own a rooted android device. There is an app called wofokill that do the job for you. Due to its potential risks,this app is no longer available on the Playstore but you can find it by googling. After installing the app you need to connect your mobile device to Wifi network .After connecting you can see all the devices connected to the network and kick any device off the wifi network(by knowing their IP). HOW THIS WORKS: When your phone is connected to the Wireless network, this app sends spoofing packets to all other devices and make then think that your phone is access point (or router). As a result, all the packets start flowing through your phone and then you can kick off them. This app will not disconnect them but only disable their Internet access and make them think that they are connected to a very slow Internet connection.